In 1878, the British researchers Arthur Downes and Thomas Blunt discovered the sterilizing effects of UV light. In 1903, the Danish physician Niels Finsen received the Nobel prize in medicine for using UV light in the treatment of skin diseases. Ultraviolet (UV) light has been used for over a hundred years to sterilize rooms, objects and the skin. However, used on skin, these high-energetic photons can cause heavy sunburns and even skin cancer. With a range of 100 - 400 nm, the UV electromagnetic spectrum lies between x-ray radiation and visible light. When high energy photons are absorbed by living organisms in the range 100 - 315 nm, they partially destroy the cellular DNA. A cell with damaged DNA cannot work efficiently. It loses its reproductive capacities and eventually dies. Therefore, UV light is considered a highly effective method to kill bacteria and viruses. Luckily, UV light can sterilize at 222 nm without damaging the human skin which makes it a safe and powerful tool to fight bacteria and viruses, including COVID-19.
Several studies (1, 2, 3) have shown that the UVC area from 200 nm to 280 nm is the most effective when it comes to sterilization. They have also shown that some UV radiation causes damage to the human skin.
Optical filters can be built so they transmit the desired UV frequency and at the same time block the damaging wavelengths.
Research (1) has shown that an emission at 222 nm from an excimer lamp can sterilize without penetrating the basal layer of the skin. The emission spectrum must be filtered to prevent damage to the patient, by blocking the longer, hazardous wavelengths. UV bandpass filters from Andover Corporation can be used to achieve this.
Andover offers UV bandpass filters that provide 40% transmission at 222 nm while blocking the longer wavelengths to 280 nm. The filters can be customized for integration into a large number of lamp configurations. We also offer budget-friendly standard optics to fit our customers’ requirements.
(1) “Germicidal Efficacy and Mammalian Skin Safety of 222nm UV Light” - February 2017, U.S. National Institute of Health national Library of Medicine
(2) “Testing Novel Inventions to Protect Workers from Airborne Infections” - January 2018, U.S. Dept. of Health & Human Services, CDC
(3) “Ultraviolet Germicidal Irradiation – Current Best Practices” – August 2008, ASHRAE Journal